Magnetically navigable and/or controllable device for removing material from body lumens and cavities

ABSTRACT

A magnetically navigable atherectomy device includes a cutting head, a flexible drive shaft having a proximal and a distal end, with the cutting device on the distal end, and a magnet associated with the cutting head, the magnet of sufficient size to allow the cutting head to be oriented by an externally applied magnetic field. The magnet may be a portion of the cutting head made from a magnetically permeable or permanent magnetic material, a portion of the drive shaft made from a magnetically permeable or permanent magnetic material; a separate magnet between the cutting head and the drive shaft, a portion a magnet on a sheath covering the drive shaft. Alternatively a guide wire can provided with a magnetic material on its distal end. Through the application of a magnetic field and/or a magnetic gradient, the artherectomy device can be guided to the location of the atheromatous material in the body. Once at the site of atheromatous material, through the application of a magnetic field or magnetic gradient, the device can be manipulated into proximity to the atheromatous material to remove the material.

FIELD OF THE INVENTION

This invention relates to devices for removing material from body lumensand cavities, and in particular to such devices that can be magneticallynavigated and/or controlled.

BACKGROUND OF THE INVENTION

There are many medical conditions where it is desirable to removematerial from the surface of a body lumen or cavity. For example in thecase of occluded blood vessels, one method of treating this condition touse a cutting tool in the blood vessel to remove accumulatedatheromatous material. These tools, frequently called atherectomydevices, typically comprise a blade or cutting bit or burr on the distalend of a flexible drive shaft. The drive shaft is preferably containedwithin a flexible sheath to protect the walls of the blood vessels fromthe rotation of the drive shaft. Examples of such devices includeShiber, U.S. Pat. No. 4,842,579, Simpson et al., U.S. Pat. No.5,047,040; and Auth et al., U.S. Pat. No. 5,314,407, incorporated hereinby reference.

An atherectomy device is typically navigated to the site of the diseaseby mechanically manipulating a guide wire to the site of the disease,and then advancing the atherectomy device over the guide wire to thesite. The navigation of the guide wire through the blood vessel can be aslow and tedious process, requiring great skill. Once at the site of thedisease, it can be difficult to precisely control the atherectomy deviceto satisfactorily remove the atheromatous material. Part of thisdifficulty arises from guide wire bias, for example as the atherectomydevice traverses bends in the blood vessels the guide wire and devicetend to move toward the outside of the bend, making it difficult toremove atheromatous material from the insides of the bends. Even instraighter segments of blood vessels, it is difficult to control theposition of the atherectomy device within the cross section of the bloodvessel, or the orientation of the cutting head of the atherectomy devicewithin the blood vessel, and thus it is difficult to form a passagethrough the vessel larger than that cross section of the tool.

SUMMARY OF THE INVENTION

The present invention relates to an atherectomy device that can bemagnetically controlled, and to the magnetic control of atherectomydevices. Generally, the atherectomy device of the present inventioncomprises a flexible drive shaft, with a cutting head on the distal endof the drive shaft. A magnet is associated with the cutting head. In oneconstruction, the cutting head itself is made of a magnetic material,either a permanent magnet or a permeable magnet. In another constructiona magnet is disposed between the cutting head and the drive shaft. Instill another construction, the distal end portion of the drive shaftadjacent the cutting head is magnetic. In still another construction, amagnet is positioned on the distal end of the sheath, in proximity tothe cutting head. The magnet can be any material with magneticproperties (i.e., responsive to a magnetic field or magnetic gradient),and may either be a separate part or constitute a magnetic portion of anexisting part.

The magnet associated with the cutting head facilitates navigation ofthe atherectomy device to the procedure site, and control of the cuttinghead at the procedure site through the application of a magnetic fieldand/or magnetic field gradient. A magnetic field can be applied toorient the atherectomy device in the blood vessel for navigating to theprocedure site. The applied magnetic field aligns the magnet associatedwith cutting head in the direction of the field, so that the atherectomydevice can be more easily steered through the blood vessels. The devicecan then be advanced in the desired direction simply by pushing on theproximal end. Alternatively, or in addition, a magnetic field gradientcan be applied to the magnet associated with the cutting head to applyforce to the atherectomy device to actually move the device through theblood vessel, or assist the mechanical pushing of the device through theblood vessel. Once at the procedure site, magnetic fields and/ormagnetic field gradients can be applied to the magnet associated withthe cutting head to control the orientation of the device and itsposition within the cross-section of the blood vessel. Thus, with theapplication of a magnetic field, the cutting portion of the cutting headcan be oriented toward the accumulated atheromatous material, and thecutting tool itself can be moved within the cross-section of the bloodvessel to act on the accumulated atheromatous material, for example onthe insides of bends. Because the tool can be both oriented and moved,the tool can open a passage in the blood vessel that is larger than thecross section of the device itself. By automating the control of thedirection and/or gradient of the applied magnetic field, the procedurecan be automated, so that once the tool is navigated to the site of thedisease, the tool is automatically precessed to clear the cross-sectionof the vessel in adjacent the atherectomy device of the atheromatousmaterial. In addition to precessing the cutting head by continuouslychanging the magnetic field, it is also possible to continuously movethe cutting head around the cross-section of the vessel by continuouslyvarying the magnetic gradient. Of course both the magnetic field andmagnetic gradient can be simultaneously changed to cause the orientationand the position of the cutting head to change to remove material fromaround the cross section of the vessel.

In accordance with another embodiment of this invention, it is alsopossible that instead of, or in addition to, associating a magnet withthe cutting head, the atherectomy device can be used in conjunction witha magnetic guide wire. A magnet can be provided on the end of aconventional guide wire, or a portion of the guide wire can be mademagnetic. The guide wire is then navigated to the diseased site. Themagnet on or in the guide wire facilitates orienting and/or moving theguide wire through the blood vessels. Once at the site, the atherectomydevice can be brought into close association with the magnet on theguide wire, and the magnet on the guide wire can be used to orient andto move the cutting head within the blood vessel.

The atherectomy device of the present invention can be quickly andeasily navigated to the site of the disease. This makes the procedureeasier on the physician and the on patient. Once at the site, the toolcan be operated more effectively, removing atheramotous material fromaround the entire circumference of the blood vessel, and clearing apassageway larger than the cross section of the atherectomy deviceitself. These and other features and advantages will be in part apparentand in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial longitudinal cross sectional view of an atherectomydevice constructed according the principles of this invention;

FIG. 2 is a partial longitudinal cross sectional view of an alternateconstruction of the atherectomy device, incorporating a discrete magnet;

FIG. 3 is a partial longitudinal cross-sectional view of an alternateconstruction of the atherectomy device, in which a portion of the driveshaft is magnetic;

FIG. 4 is a partial longitudinal cross-sectional view of an alternateconstruction of the atherectomy device, incorporating a magnet on thesheath;

FIG. 5A is a longitudinal cross-sectional view of a blood vessel showingan atherectomy device of the present invention therein before theapplication of a magnetic gradient;

FIG. 5B is a longitudinal cross-sectional view of a blood vessel showingan atherectomy device of the present invention therein during theapplication of a magnetic gradient;

FIG. 6A is a longitudinal cross-sectional view of a curved segment of ablood vessel showing an atherectomy device of the present inventiontherein, before the application of a magnetic gradient;

FIG. 6B is a longitudinal cross-sectional view of a curved segment of ablood vessel showing an atherectomy device of the present inventiontherein, during the application of a magnetic gradient;

FIG. 7 is a transverse cross section of a blood vessel showing thepossible positions of an atherectomy device of the present inventionwith the application of a magnetic gradient;

FIG. 8 is a longitudinal cross-sectional view of the blood vesselshowing a atherectomy tool oriented by a magnetic field to removeaccumulated atheromatous material;

FIG. 9A is a partial longitudinal cross sectional view of an atherectomydevice constructed according to the principles of this invention,employing a magnetic guide wire with a discrete magnet;

FIG. 9B is a partial longitudinal cross sectional view of an atherectomydevice constructed according to the principles of this invention,employing a magnetic guide wire with a magnetic portion; and

FIG. 10 is a partial longitudinal cross sectional view of an athrectomydevice constructed according to the principles of this invention withouta guide wire.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

An atherectomy device constructed according to the principles of thisinvention is indicated generally as 20 in FIG. 1. While the drawings anddescription of this preferred embodiment show and describe anatherectomy device for removing atheromatous material from the walls ofblood vessels, the invention is not so limited, and applies to anymagnetically navigable and/or controllable device for removing materialfrom the surface of a body lumen or cavity. As shown in FIG. 1, theatherectomy device 20 comprises a flexible drive shaft 22 and a cuttinghead 24. The drive shaft 22 is preferably made from a tight helicallycoiled wire. The cutting head 24 is preferably an oblate spheroid, withan abrasive, such as diamond particles on the distal end. The driveshaft 22 rotates the cutting head 24, and the abrasive on the distal endof the cutting head abrades the atheromatous material in the vessel.There is a passage 26 through cutting head 24, and through the driveshaft 22 for receiving a guide wire 28. The guide wire 28 can beadvanced in the blood vessel and then the atherectomy device 20 isadvanced over the guide wire to the procedure site. The end 30 of theguide wire 28 may have a stop 32, to prevent the guide wire from beingwithdrawn entirely into the passage 26, and to blunt the end of theguide wire so that it does not puncture the blood vessel. Of course, asdescribed below, the athrectomy device can be used without a guide wireand guided magnetically. This is particularly advantageous in totallyoccluded vessels where the guide wire cannot extend in front of theatherectomy device because of the occlusion. According to the principlesof this invention, the cutting head 24 is made from or contains amagnetic material, for example a permanent magnetic materials such asHipercoo® (available from Carpenter Steel, Reading, Pa.) or a permeablemagnetic material such as neodymium-iron-boron (Nd—Fe—B) (available fromMagstar Technologies, Minneapolis, Minn. The cutting head 24 may becoated with an abrasive material, such as diamond dust embedded in thedistal surface of the head.

The drive shaft 22 is preferably enclosed in a sheath 34, that protectsthe blood vessel from the rotating drive shaft. The sheath 34 may bemade of a conventional medical catheter material such aspolyvinylchloride.

A first alternative construction of the atherectomy device 20, indicatedas 20′, is shown in FIG. 2. The atherectomy device 20′ is similar inconstruction to atherectomy device 20, except that instead of thecutting head 24 being made from a magnetic material, a magnet 36 isdisposed between the drive shaft 22 and the cutting head 24. This magnetmay be a permanent magnetic material such as Hiperco®, or a permeablemagnetic material such as Nd—Fe—B.

A second alternative construction of the atherectomy device 20,indicated generally as 20″, is shown in FIG. 3. The atherectomy device20″ is similar in construction to atherectomy device 20, except thatinstead of the cutting head 24 being made from a magnetic material, thedistal portion 38 of drive shaft 22 is magnetic. This distal portion maybe made from a permanent magnetic material such as Hiperco® or apermeable magnetic material such as Nd—Fe—B.

A third alternative construction of the atherectomy device 20, indicatedgenerally as 20′″ is shown in FIG. 4. The atherectomy device is similarin construction to atherectomy device 20, except that instead of thecutting head 24 being made from a magnetic material, the distal portionof the sheath has a magnet 40 thereon. The magnet may be embedded in thedistal end portion of the catheter, or secured on the end, for examplewith a suitable medical grade adhesive. The cutting head can beretracted against the magnet 40, so that the magnet is closelyassociated with the cutting head 24.

Regardlesss of the means by which the magnet is associated with theatherectomy device, a magnetic field can be applied to orient theatherectomy device in the blood vessel for navigating to the proceduresite. The externally applied magnetic field may be applied, for examplewith a magnetic surgery system like that disclosed in co-pending U.S.patent application Ser. No. 08/920,446, filed Aug. 29, 1997, entitledMethod and Apparatus for Magnetically Controlling Motion Direction of aMechanically Pushed Catheter, incorporated herein by reference. Theapplied magnetic field aligns the magnet associated with cutting head,e.g., the magnetic cutting head 24 in device 20, the magnet 36associated with the cutting head in device 20′, or the magnetic distalend portion 38 of the drive shaft 22 in device 20″, in the direction ofthe field, so that the atherectomy device can be more easily steeredthrough the blood vessels. Once the distal end of the device is orientedin the desired direction of travel by the magnetic field, the device canthen be advanced in the desired direction simply by pushing on theproximal end. Alternatively, or in addition, a magnetic field gradientcan be applied to the to the magnet associated with the cutting head toapply force to the atherectomy device to actually advance the devicethrough the blood vessel. This force can be the only force used to movethe atherectomy device, or this force can merely be used to assist themechanical pushing of the device through the blood vessel.

Once at the site, magnetic fields can be applied to the magnetassociated with the cutting head to control the orientation of thedevice and its position within the cross-section of the blood vessel.Thus, with the application of a magnetic field, the cutting portion ofthe cutting head can be oriented toward the accumulated atheromatousmaterial, and the cutting tool itself can be moved within thecross-section of the blood vessel to act on the accumulated atheromatousmaterial, for example on the insides of bends. FIG. 5A shows anatherectomy device 20 in a blood vessel. The device is positionedgenerally along the guide wire 28. However, as shown in FIG. 5B upon theapplication of a magnetic field gradient, the cutting head 24 can bedrawn toward the accumulated atheromatous material, to more completelyand effectively abrade the material from the vessel wall. This techniqueis particularly advantageous in the bends of blood vessels, as shown inFIG. 6A, wherein the natural stiffness of the guide wire and the devicecauses the atherectomy device to a position away from the inside of thecurve and toward the outside of the curve. However, as shown in FIG. 6B,upon the application of a magnetic field gradient, the cutting head 24can be drawn against the accumulated atheromatous a material on theinside of the bend, to remove this material and more completely open theblood vessel. As shown in FIG. 7, by controlling the direction of theapplied magnetic gradient, it is possible to move the cutting head toany position in the cross section of the blood vessel.

As shown in FIG. 8, it is also possible to apply a magnetic field tosimply orient the cutting head 24, positioning the distal abrasivecutting surface of the cutting head against the atheromatous material onthe vessel wall. The effects of orientation with a magnetic field andpositioning with a magnetic gradient can be combined. While the gradientpulls the cutting head into the atheromatous material, the fielddirection can be along the axis of the vessel, to keep the cutting headoriented along the vessel. Alternatively, the field direction can be atan angle with respect to the vessel, to tilt the cutting head into theatheromatous material.

Further, by continuously moving the applied magnetic field, it ispossible to precess the cutting head 24 around the circumference of thevessel, moving the cutting head to clear substantially the entire crosssection of the vessel. By employing a microprocessor control, or otherautomated control to change the magnetic field as a function of time,the cutting tool can be automatically precessed within the vessel. Thusthe atherectomy tool can be used to create a flow pathway through thevessel that is actually larger than the cross section of the atherectomydevice. As the cutting head is precessing, it can be slowly advancedacross the accumulated atheromatous material. In addition to precessingthe cutting head by continuously changing the magnetic field, it is alsopossible to continuously move the cutting head around the cross-sectionof the vessel by continuously varying the magnetic gradient. Of courseboth the magnetic field and magnetic gradient can be simultaneouslychanged to cause the orientation and the position of the cutting head tochange to remove material from around the cross section of the vessel.

In accordance with a second embodiment of this invention, shown in FIG.9A and 9B, it is also possible that instead of, or in addition to,associating a magnetic with the cutting head, the atherectomy device canbe used in conjunction with a magnetic guide wire 100, having a magneticdistal end portion. As shown in FIG. 9A, the guide wire 100 has adiscrete magnet 102 on its distal end. As shown in FIG. 9B, the distalend portion 104 of the guide wire 100 is made from a magnetic wirematerial. The guide wire is then navigated to the diseased site. Themagnet on or in the guide wire facilitate orienting and/or moving theguide wire through the blood vessels. Once at the site, the atherectomydevice can be brought into close association with the magnet on theguide wire, and the magnet on the guide wire can be used to orient andto move the cutting head within the blood vessel.

In accordance with a third embodiment of this invention, shown in FIG.10, the atherectomy device can be used without any guide wire. Thedevice is navigated solely by the application of magnetic fields and/orgradients, which apply a force through the magnet associated with thecutting head. One method of navigating such an atherectomy device isthat disclosed in co-assigned U.S. Patent Application Serial No.60/095,710 filed Aug. 7, 1998, and incorporated herein by reference. Inthis method of navigation, the operating region in the patient is viewedon two planar fluoroscopic images of the operating region. The physicianidentifies the current position of the atherectomy device on eachdisplay, for example by using a mouse or similar device to point andclick on the desired location. Similarly the physician can identify thedesired new position of the atherectomy device on each display. Acomputer can control an electromagnetic system for generating anelectromagnetic field and/or gradient for orienting and/or moving thedistal end of the atherectomy device as input by the physician. Thedistal end of the atherectomy device is advanced manually orautomatically, or in some cases it can be moved by a magnetic field orgradient. In this manner, the atherectomy device can be magneticallydirected to the site of the occlusion without a guide wire, and once atthe site of the occlusion can be magnetically manipulated to remove thematerial blocking the vessel or lumen.

What is claimed:
 1. A device for removing material from the surface ofbody lumens and cavities, the device comprising: a cutting head; and amagnet configured to orient the cutting head in response to a magneticfield, the magnet of sufficient size to allow the cutting head to beoriented by an externally applied magnetic field; wherein the magnetcomprises a portion of the cutting head made from a magneticallypermeable or permanent magnetic material.
 2. A device for removingmaterial from the surface of body lumens and cavities, the devicecomprising: a cutting head; and a magnet configured to orient thecutting head in response to a magnetic field, the magnet of sufficientsize to allow the cutting head to be oriented by an externally appliedmagnetic field; the device further comprising a flexible drive shafthaving a proximal and a distal end, with the cutting head on the distalend, and wherein the magnet comprises a portion of the flexible driveshaft being made of a magnetically permeable or permanent magneticmaterial.
 3. A method of removing material from the walls of a bodylumen or cavity, comprising: introducing a tool into the lumen orcavity, the tool having a cutting head on its distal end and a magnetconfigured to orient the cutting head in response to a magnetic field;navigating the tool to the site of the material to be removed bysuccessively applying a magnetic field to orient the distal end of thetool and advancing the tool in the lumen or cavity to the site of thematerial to be removed; and operating the cutting head to remove thematerial from the surface of the lumen or cavity; wherein the magnetassociated with the cutting head is at least a part of the cutting headmade of a magnetic material.
 4. A method of removing material from thewalls of a body lumen or cavity, comprising: introducing a tool into thelumen or cavity, the tool having a cutting head on its distal end and amagnet configured to orient the cutting head in response to a magneticfield; navigating the tool to the site of the material to be removed;and operating the cutting head to remove the material from the surfaceof the lumen or cavity by applying at least a magnetic field to orientthe cutting head or a magnetic gradient to move the cutting head withinthe lumen or cavity; wherein the step of operating the cutting head toremove the material comprises applying both a magnetic field to orientthe cutting head and a magnetic gradient to move the cutting head towardthe material in the lumen or cavity.
 5. A method of removing materialfrom the walls of a body lumen or cavity, comprising: introducing a toolinto the lumen or cavity, the tool having a cutting head on its distalend and a magnet configured to orient the cutting head in response to amagnetic field; navigating the tool to the site of the material to beremoved; and operating the cutting head to remove the material from thesurface of the lumen or cavity by applying at least a magnetic field toorient the cutting head or a magnetic gradient to move the cutting headwithin the lumen or cavity; and applying a continuously changingmagnetic field to precess the cutting head within the lumen or cavity.6. The method according to claim 5 wherein the step of applying acontinuously changing magnetic field is done with a computer controlledmagnet.
 7. A method of removing material from the walls of a body lumenor cavity, comprising: introducing a tool into the lumen or cavity, thetool having a cutting head on its distal end and a magnet configured toorient the cutting head in response to a magnetic field; navigating thetool to the site of the material to be removed; and operating thecutting head to remove the material from the surface of the lumen orcavity by applying at least a magnetic field to orient the cutting heador a magnetic gradient to move the cutting head within the lumen orcavity; and applying a continuously changing magnetic gradient to movethe cutting head within the lumen or cavity.